From: Joerg Roedel <joerg.roe...@amd.com> The nested SVM code emulates a #vmexit caused by a request to open the irq window right in the request function. This is a bug because the request function runs with preemption and interrupts disabled but the #vmexit emulation might sleep. This can cause a schedule()-while-atomic bug and is fixed with this patch.
Signed-off-by: Joerg Roedel <joerg.roe...@amd.com> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index e372854..884bffc 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -85,6 +85,9 @@ struct nested_state { /* gpa pointers to the real vectors */ u64 vmcb_msrpm; + /* A VMEXIT is required but not yet emulated */ + bool exit_required; + /* cache for intercepts of the guest */ u16 intercept_cr_read; u16 intercept_cr_write; @@ -1379,7 +1382,14 @@ static inline int nested_svm_intr(struct vcpu_svm *svm) svm->vmcb->control.exit_code = SVM_EXIT_INTR; - if (nested_svm_exit_handled(svm)) { + if (svm->nested.intercept & 1ULL) { + /* + * The #vmexit can't be emulated here directly because this + * code path runs with irqs and preemtion disabled. A + * #vmexit emulation might sleep. Only signal request for + * the #vmexit here. + */ + svm->nested.exit_required = true; nsvm_printk("VMexit -> INTR\n"); return 1; } @@ -2340,6 +2350,13 @@ static int handle_exit(struct kvm_vcpu *vcpu) trace_kvm_exit(exit_code, svm->vmcb->save.rip); + if (unlikely(svm->nested.exit_required)) { + nested_svm_vmexit(svm); + svm->nested.exit_required = false; + + return 1; + } + if (is_nested(svm)) { int vmexit; @@ -2615,6 +2632,13 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) u16 gs_selector; u16 ldt_selector; + /* + * A vmexit emulation is required before the vcpu can be executed + * again. + */ + if (unlikely(svm->nested.exit_required)) + return; + svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX]; svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP]; svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP]; -- To unsubscribe from this list: send the line "unsubscribe kvm-commits" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html